docs: def is_freesurfer_subject_path(path):
      '''
      is_freesurfer_subject_path(path) yields True if the given path appears to be a valid freesurfer
        subject path and False otherwise.
      A path is considered to be freesurfer-subject-like if it contains the directories mri/, surf/,
      and label/.
      '''
      if not os.path.isdir(path): return False
      else: return all(os.path.isdir(os.path.join(path, d)) for d in ['mri', 'surf', 'label'])